[v02] REPOST powerpc/migration: Handle unitialized timer reset

[Michael Ellerman]

On Thu, 2018-09-20 at 16:45:13 UTC, Michael Bringmann wrote:
> After migration of a powerpc LPAR, the kernel executes code to
> update the system state to reflect new platform characteristics.
> Such changes include modifications to device tree properties
> provided to the system by PHYP.  Property notifications received
> by the powerpc 'migration_store' code are passed along to the
> kernel in general through a call to 'of_update_property' which
> in turn passes such events back to all modules through entries like
> the '.notifier_call' function within the NUMA module.  When the
> NUMA module updates its state, it resets its event timer.  If this
> occurs after a previous call to 'stop_topology_update' or on a
> system without VPHN enabled, the code runs into an unitialized
> timer structure and crashes.  This patch adds a safety check
> along this path toward the problem code.
> 
> Note: This crash was observed on every LPM in the 4.17-rc7 kernel
> (and in the 4.18 kernel) of a system with dedicated CPUs enabled.
> An example crash log without the patch is as follows.
> 
...
> 
> Signed-off-by: Michael Bringmann <mwb at linux.vnet.ibm.com>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/8604895a34d92f5e186ceb931b0d1b

cheers